Quote:
Originally Posted by Salavee
All good , but my question was referring to polishing a chamber, not lengthening a throat or cleaning up the leade . AFIK , a chamber is a chamber and ends pretty much at the case mouth. It has specific SAAMI or custom specs peculiar to each different cartridge. The throat and leade are actually different operations that can have arbitrary dimensions or angles and are actually part of the bore. Apart from that, I believe the bullet does contact the leade as it enters the bore (thus the angle) and after it crosses the threshold of the freebore dimension ( throat.) If I'm wrong about all this, I'm sure I will be corrected in short order.
What do you suggest regarding chamber polishing .. good idea, or not so good ?
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If a chamber is cut by a competent gunsmith with a sharp reamer here should be no need to polish the chamber as you suggest. In fact it is considered by some to be desirable not to have an over polished barrel and minimal case taper so that the brass momentarily clings to the chamber reducing bolt thrust (P.O. Ackley among others). I believe this to be true when pressures exceed Saami specifications but not necessarily that important if Saami Pressures are adhered to.
Contrary to what you believe the leade and throat are part of the chamber and are the same on all Sammi Speced chambers. If they or the neck area are changed, as in the drawing 260 Rem posted, it is not a saami speced cartridge but a custom chamber. As the leade (freebore) is larger in diameter than the bullet diameter the bullet should not contact the chamber until it reaches the lands which are just past the conical throat. Of course there could be enough contact between the bullet and leade (freebore) to cause copper transfer if the bullet runout is excessive. Here is a link to a post with picture that may help :
http://noebulletmolds.com/smf/index.php?topic=89.0